This invention generally relates to magnetostrictive materials and more particularly to materials which exhibit relatively large magnetostriction at room temperature.
Most transducers commonly in use today fall into two categories: electrostrictive and magnetostrictive. Among the electrostrictive devices are barium titanate and PZT. Among the magnetostrictive materials are Ni and Al-Fe alloys. Although these magnetostrictive materials have magnetostrictions at room temperature (which is the operating temperature of most transducer devices) which enable them to be used in transducer devices, it has always been desirable to obtain other magnetostrictive materials which have greater magnetostriction then those presently in use.
In 1963, it was discovered by A. E. Clark, R. Bozorth and B. DeSavage, Phys. Letters 5, 100 (1963), that certain heavy rare earth elements have magnetostrictions about 1000 times greater than Fe and about 200 times greater than Ni. However, these enormous magnetostrictions are only present at cryogenic temperatures and are most pronounced in the neighborhood of absolute zero. At room temperature, the rare earth elements have little magnetostriction since their magnetic ordering temperatures fall below room temperature. Therefore, all are far inferior to the hereinbefore referenced materials which are presently in use.
Thus, research has been conducted in an attempt to find materials which have relatively large magnetostriction at temperatures above 250.degree. K. and preferably at about 300.degree. K. (room temperature).
The most attractive transducer materials have high magnetostrictions and low magnetic anisotropies (i.e. they are magnetically soft). In contradistinction, the most attractive rare earth permanent magnet materials (e.g. SmCo.sub.5) have high magnetic anisotropies (i.e. they are magnetically hard).